The adrenal glands sit on top of your kidneys and are comprised of an inner medulla region that is enclosed by the outer adrenal cortex. Both portions of the adrenal gland secrete hormones that regulate body functions and help maintain internal balance.
As we learn about the endocrine system, we see that there are bits and pieces of endocrine tissue scattered about in different regions of your body. We even see endocrine glands sitting on top of each of your kidneys. In this lesson, we will learn about these unique and powerful glands that hover over the top of your kidneys, called the adrenal glands.
The adrenal glands are endocrine glands that sit right on top of the kidneys.
When you look at a picture of the kidneys, it's almost like they are wearing hats. These 'hats' are actually your adrenal glands. We can define the adrenal glands as hormone-producing glands located on top of the kidneys. When you look at a picture of one of your adrenal glands, it looks like a single organ. However, if you were to dissect the gland, you would quickly see that it's more like two endocrine glands in one.
Adrenal Cortex and Corticosteroids
The outer portion of the adrenal gland is called the adrenal cortex. It secretes steroid hormones. Steroid hormones are a class of hormones that are made from cholesterol. In today's world, cholesterol often gets a bad rap for being detrimental to heart health. But, it's interesting to learn that cholesterol actually serves a number of purposes in the body. For instance, if you did not have cholesterol, you would not be able to produce the steroid hormones from the adrenal cortex.
Without these hormones, your body would have a hard time regulating fluid and electrolyte balance and maintaining homeostasis. This is because the adrenal cortex secretes three major groups of steroid hormones that are collectively referred to as corticosteroids. This is an easy term to remember because we see that the prefix 'cortico' refers to the cortex of the adrenal gland and that the word 'steroid' is contained in the term. Therefore, we see that corticosteroids are steroid hormones secreted by the adrenal cortex.
Hormones secreted by the adrenal glands help maintain homeostasis in the body.
There are different kinds of corticosteroids that we see coming from the adrenal cortex. One kind is called mineralocorticoids. Mineralocorticoids are important hormones that help regulate the water and electrolyte balance in the body. The two most important electrolytes that are regulated are sodium and potassium. Because sodium and potassium are both minerals, it may help you to recall that mineralocorticoids are important in the regulation of minerals.
Glucocorticoids are another kind of corticosteroid that we see coming from the adrenal cortex. Glucocorticoids help regulate carbohydrate, fat and protein metabolism and have an anti-inflammatory effect on the body. It's thanks to glucocorticoids that we are able to cope with a wide range of long-term stressors. Glucocorticoid secretions will increase any time we deal with continual stress. Anything from the death of a loved one to prolonged fasting can stimulate the production of glucocorticoids.
In fact, one of the effects of glucocorticoids is to increase blood glucose levels so we have readily available glucose for energy. This fact may help you recall the term because glucocorticoids increase glucose. Also, because glucocorticoids have an anti-inflammatory property, synthetic glucocorticoids are often prescribed as drugs to treat chronic inflammatory disorders in many areas of the body, including the bowel, skin, bones and joints.
Synthetic glucocorticoids are prescribed to treat chronic inflammatory disorders.
In addition to mineralocorticoids and glucocorticoids, we also see sex hormones secreted by the adrenal cortex. The sex hormones are steroid hormones produced by the adrenal cortex that influence male and female sexual characteristics. Regardless of whether you are male or female, your adrenal cortex secretes male sex hormones as well as a small amount of female sex hormones throughout life.
Adrenal Medulla and Catecholamines
The center of the adrenal gland can be considered a separate endocrine gland from the cortex because it differs in both structure and function. This central region of the adrenal gland is called the adrenal medulla. Unlike the cortex, the medulla develops from nervous tissue, and it is stimulated to release its hormones by impulses from the sympathetic nervous system. Because of these facts, some consider the adrenal medulla to be a misplaced portion of the sympathetic nervous system.
The hormones secreted from the adrenal medulla are collectively referred to as catecholamines. Catecholamines help you deal with short-term stress. We know that the sympathetic nervous system fires when you feel threatened or under stress. This then stimulates the adrenal medulla to release catecholamines. These hormones then enter your bloodstream and essentially prolong the fight-or-flight response initiated by the sympathetic nervous system.
The catecholamines secreted from the adrenal medulla prolong the fight-or-flight response.
Your adrenal glands are hormone-producing glands located on top of your kidneys. The adrenal cortex is the outer portion of the adrenal gland that secretes steroid hormones. Collectively, the steroid hormones secreted by the adrenal cortex are called corticosteroids. One kind of corticosteroid is called mineralocorticoids. These hormones help regulate the water and electrolyte balance in the body. Another kind is called glucocorticoids. They help regulate carbohydrate, fat and protein metabolism and have an anti-inflammatory effect on the body. We also see sex hormones coming from the adrenal cortex. These are steroid hormones that influence male and female sexual characteristics.
The adrenal medulla is the central region of the adrenal gland. It is stimulated by the sympathetic nervous system to secrete catecholamines, which are hormones that help you deal with short-term stress.
Following this video lesson, you'll be able to:
- Locate the adrenal glands
- Identify the different structures of the adrenal glands
- List the groups of steroid hormones secreted by the adrenal cortex and explain their functions
- Understand how catecholamines are secreted by the adrenal medulla and describe their functions